1. Field of the Invention
This invention relates to a liquid crystal display device and a method and an apparatus of fabricating the liquid crystal display device. More particularly, this invention relates to a liquid crystal display device having an improved lift-off efficiency and a method and an apparatus of fabricating the liquid crystal display device that are adapted to improve lift-off efficiency.
2. Description of the Related Art
Generally, a liquid crystal display device (LCD) controls the light transmittance of a liquid crystal having a dielectric anisotropy by using an electric field to thereby display a picture. An LCD includes a liquid crystal display panel for displaying a picture using a liquid crystal cell matrix and a driving circuit for driving the liquid crystal display panel.
Referring to FIG. 1, a related art liquid crystal display panel includes a color filter substrate 10 and a thin film transistor substrate 20 joined together with a liquid crystal 24 therebetween.
The color filter substrate 10 may include a black matrix 4, a color filter 6 and a common electrode 8 that are sequentially provided on an upper glass substrate 2. The black matrix 4 may be provided in a matrix on the upper glass substrate 2. The black matrix 4 divides an area of the upper glass substrate 2 into a plurality of cell areas that are to be provided with the color filter 6. The black matrix 4 prevents light interference between adjacent cells and external light reflection. The color filter 6 is provided at the cell area divided by the black matrix 4 in such a manner to be divided into red (R), green (G) and blue (B) filters, thereby transmitting red light, green light and blue light. The common electrode 8 may be formed from a transparent conductive layer entirely coated onto the color filter 6, and supplies a common voltage Vcom that serves as a reference voltage upon driving the liquid crystal 24. In order to make a surface of the color filter level with that of the black matrix 4, an over-coat layer (not shown) may be provided on the color filter 6 and the black matrix 4.
The thin film transistor substrate 20 includes a thin film transistor 18 and a pixel electrode 22 provided for each cell area. The cell area is defined by a crossing between a gate line 14 and a data line 16 on a lower glass substrate 12. The thin film transistor 18 applies a data signal from the data line 16 to the pixel electrode 22 in response to a gate signal from the gate line 14. The pixel electrode 22 may be formed of a transparent conductive layer and is supplied a data signal from the thin film transistor 18 to drive the liquid crystal 24.
The liquid crystal 24 having a dielectric anisotropy is rotated according to an electric field generated by the data signal to control light transmittance. Thus, a gray scale level is implemented.
Further, the liquid crystal display panel may include an alignment film (not shown) for pre-tilting an initial aligning, and a spacer (not shown) for constantly keeping a cell gap between the color filter substrate 10 and the thin film transistor substrate 20.
In such a liquid crystal display panel, the color filter substrate 10 and the thin film transistor substrate 20 are formed by a plurality of mask processes. Herein, one mask process includes many processes such as thin film deposition (or coating), cleaning, photolithography, etching, stripping and inspection processes, etc.
Particularly, because fabricating the thin film transistor substrate includes a semiconductor process and requires a plurality of mask processes, it has a complicated fabricating process. This complicated fabricating process acts as a major factor in the increased manufacturing cost of the liquid crystal display panel. Therefore, the fabricating process of the thin film transistor substrate has progressed towards a reduction in the number of required mask processes.
For example, a method of fabricating a related art thin film transistor substrate may be modified to simplify the entire process by including a diffractive exposure mask in the fourth mask process. Moreover, in a recently developed process, the method of fabricating the thin film transistor substrate may be modified to reduce the entire process by including a lift-off process in the third mask process. Specifically, in the method of fabricating the thin film transistor substrate using the third mask process, a transparent conductive layer is initially entirely coated onto a photo-resist pattern for forming a contact hole. Then, a photo-resist pattern and the transparent conductive layer are removed by a lift-off process, thereby patterning the transparent conductive layer. For improving a lift-off efficiency, a stripper infiltration path may be implemented to enable a stripper to easily infiltrate into a transparent conductive layer coated on a photo-resist pattern.